Table 1 Comparison of the screening methods for metagenomeic libraries

• Detecting changes by enzymatic reactions (e.g. halo formation around the colonies)

• PCR or Southern hybridization based on the DNA sequence consensus

• Trapping the operon induced by a substrate and sorting using FACS

• Secures a complete form of gene or gene cluster required for desired traits

• Potentially obtains completely novel genes.

• Overcomes the limitations of the heterologous expression

• Fast and economical

• Any substrates that can be introduced into cytoplasm can be used in its native forms.

• Must satisfy the expression conditions (transcription, translation, folding, secretion) in heterologous hosts

• Requires a database and analyses of the DNA sequence consensus.

• Does not guarantee the acquisition of complete forms of genes or gene clusters.

• Sensitive to the orientation of the genes with desired traits

• Cannot use substrates that do not migrate to cytoplasm

• Sensitive to the initial FACS setting

antibiotics [9, 19-22], genes involved antibiotic resistance [9, 23, 24], agarases [15], amidases [13], amylases [15, 21, 25, 26], esterase/lipases [8, 15, 21, 27, 28], xylanases [29], 4-hydoxybutyrate dehydrogenase [30] alcohol oxidoreductases [14], pectate lyases [31]

amylases [26], polyketide synthases [32, 33]

Benzoate-degratative or catechol degradative operon, P450 enzyme [16]